When cooling air is supplied to cool rotating components, such as turbine blades and the like, it is preferably fed, respectively blown with pre-swirl in the direction of rotation to a component to be cooled in order to reduce efficiency losses caused by flow turbulences. These types of known cooling-air supply devices are used as part of an intermediate turbine housing, for example, the axial bounding walls being in the form of cast or forged parts in which obliquely extending cooling air bores are provided as cooling-air outlet orifices.
It is complex and, therefore, costly to manufacture such a design that includes turned forged parts or cast parts having the respective cooling air bores. Certain wall thicknesses are necessitated by a ratio to be realized between the diameter and the length of the cooling air bores, so that such cast, respectively forged parts are high in weight. In particular, the wall thickness must also be dimensioned to allow the introduced cooling air bores to maintain the overall stability of the bounding wall for the desired range of application in a gas turbine.